diff --git a/core/hw/sh4/dyna/blockmanager.cpp b/core/hw/sh4/dyna/blockmanager.cpp
index 008345abe..1a72a7219 100644
--- a/core/hw/sh4/dyna/blockmanager.cpp
+++ b/core/hw/sh4/dyna/blockmanager.cpp
@@ -408,7 +408,18 @@ void bm_Reset()
 	protected_blocks = 0;
 	unprotected_blocks = 0;
 
-	mem_region_unlock(virt_ram_base + 0x0C000000, 0x10000000 - 0x0C000000);
+	// Windows cannot lock/unlock a region spanning more than one VirtualAlloc or MapViewOfFile
+	// so we have to unlock each region individually
+	// No need for this mess in 4GB mode since windows doesn't use it
+#if RAM_SIZE == 16 * 1024 * 1024
+	mem_region_unlock(virt_ram_base + 0x0C000000, RAM_SIZE);
+	mem_region_unlock(virt_ram_base + 0x0D000000, RAM_SIZE);
+	mem_region_unlock(virt_ram_base + 0x0E000000, RAM_SIZE);
+	mem_region_unlock(virt_ram_base + 0x0F000000, RAM_SIZE);
+#else
+	mem_region_unlock(virt_ram_base + 0x0C000000, RAM_SIZE);
+	mem_region_unlock(virt_ram_base + 0x0E000000, RAM_SIZE);
+#endif
 	if (_nvmem_4gb_space())
 	{
 		mem_region_unlock(virt_ram_base + 0x8C000000, 0x90000000 - 0x8C000000);